I suggest you take a look at McMaster-Carr part number 7877K55. I think it's around $25 and, assuming you can solder on your own electrical connector, it has the right specifications.
John at Transolve Inc. modified a Minifire to handle the longest possible fill time on an M hybrid on a hot day. Might say it has a 100% duty cycle. It is a wireless remote control, fill, fire/O2, and, dump/continuity with beeper. It has a small device like a garage door opener to control the base stations with 3 channels. It is good for 800', and more distance with the base station up off the ground 4'. The base station has an on/off key for safety. It can also launch 3 AP rockets, each separately. Only 3, 8' wires are going to the launcher/solenoids, and one short one to connect the battery. No long rolls of wire to play out, or huge automotive battery. I am using a small sealed, lead acid Harley motorcycle battery. I have tested the battery/Minifire and can get 10 launches on a hybrid...maybe more! I have fired a 29mm Sky Ripper with it, and am very pleased with the product.
www.transolve.com